1. Field of the Invention
This invention relates to an input-output unit comprising a liquid crystal display panel, EL, etc., (user interface unit) widely used with office automation machines such as copies, facsimiles, and printers and electronic machines such as personal computers, wordprocessors, handy terminals, and portable information communication machines.
2. Description of the Related Art
Known as a conventional input-output unit used for a control panel, etc., of an office automation machine such as a copier or facsimile or an electronic machine is a unit comprising an information input display of a liquid crystal display screen, etc., for displaying operation information of the machine and virtual operation buttons responsive to the operation information and enabling the operator to enter control information such as function selection or specification of the number of copies in the machine by pressing any of the virtual operation buttons.
Techniques related to such an input-output unit are already proposed, for example, as disclosed in Japanese Utility Model Laid-Open Nos. Sho 62-139025 and Hei 3-124542, Japanese Patent Laid-Open Nos. Hei 6-332602 and Sho 63-247819, etc.
Operation panel switches according to Japanese Utility Model Laid-Open No. Sho 62-139025 are operation panel switches for producing multiple display and are membrane switches having transparent electrodes placed on the top face of a dot matrix liquid crystal display device.
A switch mechanism using a liquid crystal display panel according to Japanese Utility Model Laid-Open No. Hei 3-124542 for controlling various functions of an electronic machine comprises a liquid crystal display panel for displaying symbols representing various functions of an electronic machine, a memory section for storing symbols displayed on a number of screens, a transparent pressure-sensing sensor being disposed on the front of the liquid crystal panel and switched to a function responsive to a displayed symbol group, an interface section for switching the function of the pressure-sensing sensor, and a backlight for illuminating the liquid crystal display panel from the rear.
Further, an information processing system according to Japanese Patent Laid-Open No. Hei 6-332602 comprises a liquid crystal display for displaying various pieces of information, a pressure-sensitive touch panel placed on the front of the liquid crystal display, a software keyboard being displayed on the liquid crystal display whenever necessary for receiving the coordinate position entered on the display from the pressure-sensitive touch panel, and a keyboard input auxiliary section being placed on or removed from the software keyboard and provided on the top face with projections like key buttons matched with the key layout of the software keyboard, characters matched with the key character layout of the software keyboard being displayed on the surfaces of the projections by printing, etc.
On the other hand, a touch panel input-output unit according to Japanese Patent Laid-Open No. Sho 63-247919 comprises a display unit having a display screen as a set of a large number of character areas and digital touch switches like a matrix superposed on the screen with the size of one partition area for sensing one coordinate position almost equaling the partition of the character area and the display pitch of the character areas of the display unit almost equaling the detection pitch of the partition areas of the digital switches, wherein the partition areas of the digital switches are placed on the character areas of the display unit in offset overlapped relation of 1/2 pitch in X and Y directions.
FIG. 24 is an exploded view to show a specific structure of a control panel of a conventional copier in various proposed techniques as described above. In such a conventional structure, an information input display consists of a translucent liquid crystal display screen 21 formed by bonding plate glasses and a touch panel 22 superposed on the display screen 21, and a panel board 24 having an opening 23 covers the information input display. The touch panel 22 is provided by forming a transparent conductive thin film matrix of ITO, etc., at predetermined pitches (for example, 4-mm pitches) on two glass substrates and then bonding the glass substrates with a slight gap between. When any position on the touch panel 22 is pressed, opposed conductive thin films are brought into local contact with each other by the press pressure, producing electric conduction. Then, a CPU circuit 25 determines the press position on the touch panel 22 based on a level change of an output signal. In FIG. 27, numeral 26 is a fluorescent lamp for illuminating the liquid crystal display screen 21 from behind, numeral 27 is a light diffusion board for diffusing illumination light of the fluorescent lamp 26 onto the full face of the liquid crystal display screen 21, and numeral 28 is an inverter circuit for turning on the fluorescent lamp 26.
In such a conventional information input display, if virtual operation buttons responsive to the available functions of the machine are displayed on the liquid crystal display screen 21 and the user Is made to press the operation buttons, the user presses any of the operation buttons. Thus, whether or not one of the virtual operation button is pressed can be checked from the relationship between the press position on the touch panel 22 and the display position of the virtual operation button. Therefore, in a conventional control panel having the information input display, the display contents of the liquid crystal display screen 21 are changed for each use function, whereby more than one function can be assigned to one virtual operation button, so that the number of physical operation buttons provided on the control panel can be decreased markedly.
However, since the touch panel is placed on the front of the liquid crystal display screen in the conventional information input display, contrast of the display screen lowers and the display contents are hard to see. To consider easy-to-see display contents, the liquid crystal display screen is made translucent as described above and a backlight must be provided on the rear side of the display screen.
Since the touch panel and liquid crystal display screen use glass substrates, if the user strongly presses the touch panel in such a situation that the sensitivity of the touch panel worsens, it is also feared that the glass substrates may be broken under press pressure.
On the other hand, if operation buttons frequently used like ten digit keys for entering the number of copies are displayed as virtual operation buttons on the information input display, the appearance of the control panel is uncluttered, but it is feared that operability will worsen. Thus, as shown in FIG. 24, in the conventional control panel, operation buttons 29 such as ten-digit keys frequently used are provided separately from the information input display and of course, a switch matrix board 31 on which input switches 30 are placed is disposed below the operation buttons 29. Since the switch matrix board 31 and the touch panel 22 are disposed side by side, if they can be formed in one piece, assembling the control panel is facilitated and lowering the manufacturing cost can also be expected.
Although input switches 30 of any structure may be placed on the matrix switch board 31 covered by the panel board 24 if they can convert press pressure of the operation buttons into an electric signal, there is a restriction that the touch panel must be transparent. If the control panel is manufactured with both the switch matrix board 31 and the touch panel 22 formed in one piece, the manufacturing cost increases.
To protect liquid crystal panels from press pressure, the inventor et al. examined techniques of combining a liquid crystal panel and a cushioning material and have found that a large number of patent applications were conducted as disclosed in Japanese Patent Laid-Open Nos. Hei 7-114010, Hei 6-75210, Hei 6-75213, Hei 6-75701, Hei 8-327975, Hei 6-337411, Hei 7-209635, etc.
A liquid crystal display unit according to Japanese Patent Laid-Open No. Hei 7-114010 comprises a liquid crystal display section having a liquid crystal display device, a light transmission section being disposed on the display side of the liquid crystal display section for transmitting light, and a shock-absorption section being placed between the light transmission section and the liquid crystal display section and made of a material having a refractive index closer to the refractive index of the light transmission section than that of air and having flexibility to the degree that it can substantially absorb deformation of the light transmission section.
Techniques for liquid crystal display units and manufacturing methods therefor are proposed in Japanese Patent Laid-Open Nos. Hei 6-75210, Hei 6-75213, Hei 6-75701, Hei 8-327975, etc.
Among them, the liquid crystal display unit according to Japanese Patent Laid-Open No. Hei 6-75213 comprises a liquid crystal display panel provided with a tablet board for enabling handwritten input, wherein the liquid crystal display panel and a transparent protection board on the view side of the display panel are bonded with a transparent viscous adhesive resin having a cushioning property and wherein the refractive index difference between the bond layer and the bonded members is 0.2 or less.
The liquid crystal display unit according to Japanese Patent Laid-Open No. Hei 8-327975 comprises a tablet board brought into intimate contact with the view side of a liquid crystal display panel via a weakly adhesive, transparent resin sheet having a cushioning property.
Further, in a light dispersion prevention structure and a manufacturing method therefor in a liquid crystal display unit according to Japanese Patent Laid-Open No. Hei 6-337411 comprising liquid crystal cells, a shock absorption layer being formed on the liquid crystal cell surface side, and a protection panel separated by the shock absorption layer from the liquid crystal cells with a gap of a given thickness between, the shock absorption layer is formed of a light dispersion prevention material and is bonded intimately to the liquid crystal cells and the protection panel in deaeration relation.
Further, in a light dispersion prevention structure and a manufacturing method therefor in a liquid crystal display unit according to Japanese Patent Laid-Open No. Hei 7-209635 comprising liquid crystal cells, a shock absorption layer being formed on the liquid crystal cell surface side, and a protection panel separated by the shock absorption layer from the liquid crystal cells with a gap of a given thickness between, the shock absorption layer is formed of a light dispersion prevention material and is bonded intimately to the liquid crystal cells and the protection panel in a sealed condition in deaeration relation and the protection panel is made of a synthetic resin with a hard layer at least on the surface.
However, in the techniques, if the cushioning material is inserted between the liquid crystal display panel and the polarizing panel and moreover the liquid crystal display panel and the polarizing panel are supported on the surroundings, an air layer exists between the liquid crystal display panel and the polarizing panel and light incident from the top of the polarizing panel is fully reflected in the gap between the liquid crystal display panel and the polarizing panel because of the refractive index difference between the polarizing plate and air, making the liquid crystal display panel poor in viewability. That is, a new problem arises.
In every technique proposed, the input switches are placed on the top of the liquid crystal display panel. Thus, the following problems remain unsolved: The input switches placed on the top cause the display screen contrast to lower, making the display contents hard to view, and the liquid crystal display screen must be made translucent and a backlight must be provided on the rear side to consider the easiness to read the display contents. Since the touch panel and the liquid crystal display screen use glass substrates, if the user strongly presses the touch panel in such a situation that the viewability of the touch panel worsens, it is feared that the glass substrates may be broken under press pressure even if the shock absorbing layer is provided; the problem also remains unsolved.